The inner surface layer of a shield wall of a reactor which has long been in operation is generally radioactively contaminated. In the process of demolishing such a wall in connection with the removal of such a reactor, it is a usual practice to employ a remotely operable demolishing apparatus.
A prior-art demolishing apparatus of this type is disclosed in Japanese Published Unexamined Patent Application No. 59-27297.
This prior-art apparatus has a pillar extending from above the top of the reactor toward the bottom thereof and cutting devices mounted up and down movably on the pillar for cutting the reactor shield wall. Each cutting device is retractably laterally extensible, that is, extensible toward and retractable from the shield wall, and is swingable around the pillar. In this known demolishing apparatus, the cutting device has a complex gear mechanism incorporated in it for allowing such up-and-down and swinging movement of the cutting device.
Now, demolishing work for removal of a reactor is generally carried out over a long period of time, and meanwhile, the demolishing apparatus must be subject to periodic maintenance and inspection. In view of this, therefore, it is desirable that a driving portion of the apparatus should be positioned at the top of the reactor so as to permit easy access thereto for inspection and to minimize the possibility of being exposed to radioactive contamination.
From this standpoint, the construction of the known demolishing apparatus has a drawback in that the drive mechanism, i.e., the gear mechanism for the cutting device, is incorporated in the cutting device itself. Accordingly, it is an object of the invention to provide an apparatus for demolishing a reactor shield wall wherein a mechanism for driving cutting devices may be mounted on the top of the reactor. More specifically, the object of the invention is to provide a shield wall demolishing apparatus such that a drive mechanism for swinging cutting devices may be allowed to remain located on the top of the reactor.